Phosphor converter structures for thin film packages and method of manufacture

ABSTRACT

Light emitting devices (LEDs) and methods of manufacturing LEDs are described. A method includes providing a layer of a wavelength converting material on a temporary tape. The wavelength converting material includes at least a binder or matrix material, particles of a non-luminescent material, and phosphor particles and has a concentration of 60%-90% by volume particles of the non-luminescent material and phosphor particles. The layer of the wavelength converting material is separated on the temporary tape to form multiple wavelength converting structures, which are provided on an array type frame. Heat and pressure are applied to the wavelength converting structures on the array type frame.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/142,247 filed Sep. 26, 2018, which is incorporated herein byreference in its entirety.

BACKGROUND

Semiconductor light-emitting devices or optical power emitting devices(such as devices that emit ultraviolet (UV) or infrared (IR) opticalpower), including light emitting diodes, resonant cavity light emittingdiodes, vertical cavity laser diodes, and edge emitting lasers, areamong the most efficient light sources currently available. Due to theircompact size and lower power requirements, for example, semiconductorlight or optical power emitting devices (referred to herein as LEDs forsimplicity) are attractive candidates for light sources, such as cameraflashes, for hand-held battery-powered devices, such as cameras and cellphones. They may also be used, for example, for other applications, suchas for automotive lighting, torch for video, and general illumination,such as home, shop, office and studio lighting, theater/stage lightingand architectural lighting. A single LED may provide light that is lessbright than a typical light source, and, therefore, arrays of LEDs maybe used for such applications.

SUMMARY

Light emitting devices (LEDs) and methods of manufacturing LEDs aredescribed. A method includes providing a layer of a wavelengthconverting material on a temporary tape. The wavelength convertingmaterial includes at least a binder or matrix material, particles of anon-luminescent material, and phosphor particles and has a concentrationof 60%-90% by volume particles of the non-luminescent material andphosphor particles. The layer of the wavelength converting material isseparated on the temporary tape to form multiple wavelength convertingstructures, which are provided on an array type frame. Heat and pressureare applied to the wavelength converting structures on the array typeframe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of an example method of manufacturing a lightemitting device (LED);

FIGS. 2A, 2B, 2C, 2D, 2E, 2F and 2G are diagrams of the example LED atvarious stages during the manufacturing process;

FIG. 3A is a diagram of an example LED die;

FIG. 3B is a diagram of an example light emitting semiconductorstructure that may be included in the LED die of FIG. 3A; and

FIG. 3C is a diagram of an example LED that may include the LED die ofFIG. 3A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Applications, such as the camera flash, automotive lighting and generallighting mentioned above, may make use of light emitting devices (LEDs)as white light sources. Such LEDs may be referred to as white LEDs.White LEDs may appear to emit white light from the perspective of theviewer when the LEDs are in an on state. However, they may actually bemade up of light emitting semiconductor structures that emit non-whitepump light (e.g., blue or UV light) as well as wavelength convertingstructures that make the non-white pump light appear white to theviewer.

In some applications, such as where arrays of LEDs are used, it may bedesirable to prevent un-converted pump light and converted light fromseeping through lateral sides of the LEDs and, for example, intoadjacent LEDs. In such applications, reflectors may sometimes bedisposed adjacent the side edges of each LED to prevent light fromescaping the LED through the sides. Conventionally, these reflectors arethick (e.g., over 25 microns thick) to prevent the pump light fromseeping through. However, it may also be possible to coat the sidesurfaces of LEDs with a non-metallic, thin film reflector, such as aBragg reflector, which may be much thinner (e.g., 1-10 microns thick).Use of non-metallic, thin film reflectors may be desirable inapplications such as where close placement of LEDs is required.

Non-metallic, thin film reflectors are typically made from materials,such as AlOx, TiO2, TaO2, SiO2, Nb2O5, etc., which have low coefficientsof thermal expansion (CTEs ˜6-20 ppm) in comparison to materials, suchas phosphor in glass or ceramic phosphor, that conventionally form thewavelength converting structures. If a non-metallic, thin film reflectoris coated on side surfaces of an LED that includes a light emittingsemiconductor structure and a wavelength converting structure, thenon-metallic, thin film reflector may crack due to CTE mismatch betweenthe non-metallic, thin film reflector and the wavelength convertingstructure.

In embodiments described herein, wavelength converting structures may beformed from a wavelength converting material that is highly loaded andhas a better CTE match with non-metallic, thin film reflector materialsthan the conventional wavelength converting materials described above.Such highly loaded wavelength converting material may be a moldingcompound formed from a binder or matrix material, such as silicone, thatis highly loaded with phosphor particles as well as solid particles of anon-luminescent material, such as silica (SiO₂ in amorphous orcrystalline form). A concentration of solids (the phosphor and solid,non-luminescent particles) in the molding compound may be 60%-90% byvolume.

While such a highly loaded wavelength converting material may provide abetter CTE match for non-metallic, thin film reflector materials, due tothe high concentration by volume of solids in the wavelength convertingmolding compound, when the material is sawed into individual wavelengthconverting structures for attachment to individual LED dies, the edgesbecome rough (e.g., 300-1,000 or more nm roughness). Phosphor structureswith such highly rough side edges may be incompatible for use inconjunction with non-metallic, thin film reflectors because the highlyrough side surfaces will cause light incident thereon to re-direct andleak through the non-metallic, thin film reflector and out through theside surfaces of the LED. Embodiments described herein provide methodswhereby a highly loaded wavelength converting structure, such asdescribed above, may be manufactured to have sufficiently smooth sidesurfaces (e.g., 100 nm roughness or less). While embodiments aredescribed herein with respect to a highly loaded wavelength convertingmaterial, one of ordinary skill in the art will recognize that themethods described herein may be used with any type of wavelengthconverting structure where surface smoothness is desirable.

FIG. 1 is a flow diagram 100 of an example method of manufacturing anLED. FIGS. 2A, 2B, 2C, 2D, 2E, 2F and 2G are diagrams of the example LEDat various stages during the manufacturing process.

In the example illustrated in FIG. 1, a layer of wavelength convertingmaterial is provided on a temporary tape (102). The wavelengthconverting material may be a molding compound formed from a binder ormatrix material, such as silicone, that is highly loaded with phosphorparticles as well as solid particles of a non-luminescent material, suchas silica (SiO₂). A concentration of solids (the phosphor andnon-luminescent particles) in the molding compound may be between 60 and90% by volume. The temporary tape may be any suitable sawing tape. FIG.2A is a diagram of an example 200A of a layer of a wavelength convertingmaterial 204 disposed on a temporary tape 202.

In embodiments, the wavelength converting material may be formed for usewith a semiconductor structure that emits blue light. In suchembodiments, the wavelength converting material may include, forexample, particles of a yellow emitting wavelength converting materialor green and red emitting wavelength converting materials, which willproduce white light when the light emitted by the respective phosphorscombines with the blue light emitted by the light emitting semiconductorstructure. In other embodiments, the wavelength converting material maybe formed for use with a semiconductor structure that emits UV light. Insuch embodiments, the wavelength converting material may include, forexample, particles of blue and yellow wavelength converting materials orparticles of blue, green and red wavelength converting materials.Wavelength converting particles emitting other colors of light may beadded to tailor the spectrum of light emitted from the LED.

In embodiments, the luminescent, solid particles in the wavelengthconverting material may be composed of Y₃Al₅O₁₂:Ce³⁺. The luminescent,solid particles may be an amber to red emitting rare earthmetal-activated oxonitridoalumosilicate of the general formula(Ca_(1-x-y-z)Sr_(x)Ba_(y)Mg_(z))_(1-n)(Al_(1-a+b)Ba)Si_(1-b)N_(3-b)O_(b):RE_(n) wherein 0≤x≤1, 0≤y≤1, 0≤z≤1,0≤a≤1, 0≤b≤1 and 0.002≤n≤0.2, and RE may be selected from europium(II)and cerium(III).

In other embodiments, the luminescent, solid particles in the wavelengthconverting material may include aluminum garnet phosphors with thegeneral formula (Lu_(1-x-y-a-b)Y_(x)Gd_(y))₃(Al_(1-z)Ga_(z))₅O₁₂:Ce_(a)Pr_(b), wherein 0<x<1, 0<y<1, 0≤z≤0.1, 0<a≤0.2 and 0≤b≤0.1, suchas Lu₃Al₅O₁₂:Ce³⁺ and Y₃Al₅O₁₂:Ce³⁺, which emits light in theyellow-green range; and(Sr_(1-x-y)Ba_(x)Ca_(y))_(2-z)Si_(5-a)Al_(a)N_(8-a)O_(a):Eu_(z) ²⁺,wherein 0≤a<5, 0≤x≤1, 0≤y≤1, and 0≤z≤1 such as Sr₂Si₅N₈:Eu²⁺, whichemits light in the red range. Other green, yellow and red emittingphosphors may also be suitable, including(Sr_(1-a-b)Ca_(b)Ba_(c))Si_(x)N_(y)O_(z):Eu_(a) ²⁺; (a=0.002-0.2,b=0.0-0.25, c=0.0-0.25, x=1.5-2.5, y=1.5-2.5, z=1.5-2.5) including,SrSi₂N₂O₂:Eu²⁺;(Sr_(1-u-v-x)Mg_(u)Ca_(v)Ba_(x))(Ga_(2-y-z)Al_(y)In_(z)S₄):Eu²⁺including, for example, SrGa₂S₄:Eu²⁺; Sr_(1-x)Ba_(x)SiO₄:Eu²⁺; and(Ca_(1-x)Sr_(x))S:Eu²⁺ wherein 0≤x≤1 including, CaS:Eu²⁺ and SrS:Eu²⁺.Other suitable phosphors include, CaAlSiN₃:Eu²⁺, (Sr,Ca)AlSiN₃:Eu²⁺, and(Sr, Ca, Mg, Ba, Zn)(Al, B, In, Ga)(Si, Ge)N₃:Eu²⁺.

In other embodiments, the luminescent, solid particles in the wavelengthconverting material may also have a general formula(Sr_(1-a-b)Ca_(b)Ba_(c)Mg_(d)Zn_(e))Si_(x)N_(y)O_(z):Eu_(a) ²⁺, wherein0.002≤a≤0.2, 0.0≤b≤0.25, 0.0≤c≤0.25, 0.0≤d≤0.25, 0.0≤e≤0.25, 1.5≤x≤2.5,1.5≤y≤2.5 and 1.5≤z≤2.5. The luminescent, solid particles in thewavelength converting material may also have a general formula ofMmAaBbOoNn:Zz where an element M is one or more bivalent elements, anelement A is one or more trivalent elements, an element B is one or moretetravalent elements, O is oxygen that is optional and may not be in thephosphor plate, N is nitrogen, an element Z that is an activator,n=2/3m+a+4/3b−2/3o, wherein m, a, b can all be 1 and o can be 0 and ncan be 3. M is one or more elements selected from Mg (magnesium), Ca(calcium), Sr (strontium), Ba (barium) and Zn (zinc), the element A isone or more elements selected from B (boron), Al (aluminum), In (indium)and Ga (gallium), the element B is Si (silicon) and/or Ge (germanium),and the element Z is one or more elements selected from rare earth ortransition metals. The element Z is at least one or more elementsselected from Eu (europium), Mg (manganese), Sm (samarium) and Ce(cerium). The element A can be Al (aluminum), the element B can be Si(silicon), and the element Z can be Eu (europium).

The luminescent, solid particles in the wavelength converting materialmay also be an Eu²⁺ activated Sr—SiON having the formula(Sr_(1-a-b)Ca_(b)Ba_(c))Si_(x)N_(y)O_(x):Eu_(a), wherein a=0.002-0.2,b=0.0-0.25, c=0.0-0.25, x=1.5-2.5, y=1.5-2.5.

The luminescent, solid particles in the wavelength converting materialmay also be a chemically-altered Ce: YAG (Yttrium Aluminum Garnet)phosphor that is produced by doping the Ce: YAG phosphor with thetrivalent ion of praseodymium (Pr). The luminescent, solid particles inthe wavelength converting material may include a main fluorescentmaterial and a supplemental fluorescent material. The main fluorescentmaterial may be a Ce: YAG phosphor and the supplementary fluorescentmaterial may be europium (Eu) activated strontium sulfide (SrS) phosphor(“Eu:SrS”). The main fluorescence material may also be a Ce: YAGphosphor or any other suitable yellow-emitting phosphor, and thesupplementary fluorescent material may also be a mixed ternarycrystalline material of calcium sulfide (CaS) and strontium sulfide(SrS) activated with europium ((Ca_(x)Sr_(1-x))S:Eu²⁺). The mainfluorescent material may also be a Ce:YAG phosphor or any other suitableyellow-emitting phosphor, and the supplementary fluorescent material mayalso be a nitrido-silicate doped with europium. The nitrido-silicatesupplementary fluorescent material may have the chemical formula(Sr_(1-x-y-z)Ba_(x)Ca_(y))₂Si₅N₈:Eu_(z) ²⁺ where 0≤x, y≤0.5 and 0≤z≤0.1.

In embodiments, the luminescent, solid particles in the wavelengthconverting material may include strontium-lithium-aluminum: europium(II) ion (SrLiAl₃ N₄:Eu²⁺) class (also referred to as SLA), includingMLiAl₃N₄: Eu²⁺ (M=Sr, Ba, Ca, Mg). In a specific embodiment, theluminescent particles may be selected from the following group ofluminescent material systems: MLiAl₃N₄:Eu (M=Sr, Ba, Ca, Mg), M₂SiO₄:Eu(M=Ba, Sr, Ca), MSe_(1-x)S_(x):Eu (M=Sr, Ca, Mg), MSr₂S₄:Eu (M=Sr, Ca),M₂SiF₆:Mn (M=Na, K, Rb), M₂TiF₆:Mn (M=Na, K, Rb), MSiAlN₃:Eu (M=Ca, Sr),M₈Mg(SiO₄)₄Cl₂:Eu (M=Ca, Sr), M₃MgSi₂O₈:Eu (M=Sr, Ba, Ca), MSi₂O₂N₂:Eu(M=Ba, Sr, Ca), M₂Si_(5-x)Al_(x)O_(x)N_(8-x):Eu (M=Sr, Ca, Ba). However,other systems may also be of interest and may be protected by a coating.Also combinations of particles of two or more different luminescentmaterials may be applied, such as e.g. a green or a yellow luminescentmaterial in combination with a red luminescent material.

In embodiments, the wavelength converting material may include a blendof any of the above-described phosphors.

Materials and concentrations of the non-luminescent, solid particles maybe chosen at least in part based on the chosen phosphor or phosphorssuch that the molding compound has a CTE that matches or closely matchesthe CTE of a non-metallic, thin film reflector that is to be coated onside surfaces of the light emitting semiconductor structure andwavelength converting structure. The CTE of the molding compound can bearound 20 PPM if the loading is close to 90%. Further, in order tomaximize the optical performance, by minimizing the scattering in themolding compound, the refraction index of the inert material may bematched as close as possible to the refraction index of the binder. Forexample, the refraction index of the binder may be 1.5, and therefraction index of the SiO2 is 1.46. For another example, a binder witha refraction index of 1.41 may be used in combination with SiO2. Thevolume % may calculated by taking into account of the mass of each ofthe solid components plus the mass of the binder divided and thespecific gravity of each component.

Referring back to FIG. 1, the layer of the wavelength convertingmaterial may be sawed or otherwise separated into individual wavelengthconverting structures (104). FIG. 2B is a diagram of an example of theindividual wavelength converting structures 204 disposed on thetemporary tape 202 after sawing or separation. Both a side view 200B anda top view 200C of the tape 202 are provided in FIG. 2B. In the sideview 200B, five wavelength converting structures 204A, 204B, 204C, 204Dand 204E are shown provided on the temporary tape 202. In the top view200C, nine wavelength converting structures are shown, including thewavelength converting structures 204A, 204B and 204C. While five andnine wavelength converting structures are illustrated in views 200B and200C in FIG. 2B, one of ordinary skill in the art will recognize thatthe wavelength converting layer 204 may be separated into any number ofwavelength converting structures on the temporary tape 202 within thescope of the embodiments described herein. As mentioned above, at thispoint in the process, due, for example, to displacement of particles inthe highly loaded wavelength converting molding compound, side edges(e.g., 250A, 250B, 250C and 250D as labeled for one of the wavelengthconverting structures in top view 200C of FIG. 2B) may have anundesirably high roughness, such as 300-1,000 or more nm roughness.

The individual wavelength converting structures may be transferred fromthe temporary tape 202 (106). FIGS. 2C and 2D are diagrams 200D and 200Eshowing the wavelength converting structures 204A, 204B and 204C aftertransfer. In the example illustrated in FIG. 2C, the wavelengthconverting structures 204A, 204B and 204C are provided on a structure,which may be formed from a metal frame 210 that is adhered to anothertape 206, such as a Kapton tape, via a thermal release tape or layer208. In the example illustrated in FIG. 2D, the frame 210 includesraised regions that define recessed areas 260 in which respectivewavelength converting structures are to be compressed. While not visiblein the side view in FIG. 2D, the raised regions may form an array suchthat each individual wavelength converting structure is disposed in arespective recessed area 260 in the frame 210. A release film 214 may bestretched over the frame 210 and the individual wavelength convertingstructures 204A, 204B and 204C.

The individual wavelength converting structures may be compressionmolded on the tape 206 and within the frame 210 (108). In embodiments,the structure, including the tape 206, the thermal release tape or layer208, and the metal frame 210 may be placed within a diaphragm 216 andsubjected to pressure and heat sufficient to cause the individualwavelength converting structures to flow within the respective recessedareas 260A, 260B and 260C. In embodiments, an effective pressure may bein a range of 0.7-0.8 Mpa and an effective heat may be in a range of50-90° C.

FIG. 2E is a diagram 200F of the wavelength converting structures aftercompression using the diaphragm 216. As illustrated, individualwavelength converting structures 218A, 218B and 218C take the shape ofthe respective recessed areas 260A, 260B and 260C in which they aredisposed. The raised portions of the frame 210 may have smooth innerwalls 213 such that the individual wavelength converting structures 218,after compression, will have smooth edges (e.g., 100 nm roughness orless) that are, for example, suitable for use with a thin film reflectorsuch as a Bragg reflector (not shown).

A respective light emitting die may be attached to each individualwavelength converting structure (110). In embodiments, the wavelengthconverting molding compound may have enough adhesion such that the lightemitting dies may be attached thereto without any additional adhesive.The dice may thus be attached using heat to the individual wavelengthconverting structures, such as by using the heated collet of a dieattach machine. Conventionally, a wavelength converting structure wouldbe attached to a die using some type of intervening adhesive material,which may cause wave guiding at the interface with the adhesivematerial. Because the wavelength converting structures formed using theabove-mentioned materials and using the methods described above may havesufficient adhesion such that the intervening adhesive material is notneeded, such light guiding may be eliminated, further reducing thepotential for light leakage through the sides of the LEDs and any thinfilm reflector coated thereon.

The dies may then be cured, for example, at a temperature of 150° C.over eight hours. FIG. 2F is a diagram 200G of individual LEDs 270A,270B and 270C after attaching the light emitting dies 230A, 230B and230C to their respective wavelength converting structures 218A, 218B and218C and subsequent curing. The individual LEDs 270A, 270B and 270C maythen be released from the frame 210, for example, by heating the thermalrelease tape or layer 208 (112). FIG. 2G is a diagram 200H showing LEDs270A, 270B and 270C, attached to the tape 206, formed by the method 100.

FIG. 3A is a diagram of an example LED die 230 that may be attached to awavelength converting structure, as described above. In the exampleillustrated in FIG. 3A, the LED die 230 includes a light emittingsemiconductor structure 302. Contacts 304 and 306 may be coupled to thelight emitting semiconductor structure 302, either directly or viaanother structure such as a submount, for electrical connection to acircuit board or other substrate or device. In embodiments, the contacts304 and 306 may be electrically insulated from one another by a gap 308,which may be filled with a dielectric material.

The light emitting semiconductor structure 302 may be any light emittingsemiconductor structure that emits light that may be converted to lighthaving a different color point via a wavelength converting material. Forexample, the light emitting semiconductor structure 302 may be formedfrom III-V semiconductors including, but not limited to, AlN, AlP, AlAs,AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, II-VI semiconductorsincluding, but not limited to, ZnS, ZnSe, CdSe, CdTe, group IVsemiconductors including, but not limited to Ge, Si, SiC, and mixturesor alloys thereof. These example semiconductors have indices ofrefraction ranging from about 2.4 to about 4.1 at the typical emissionwavelengths of LEDs in which they are present. For example, III-Nitridesemiconductors, such as GaN, have refractive indices of about 2.4 at 500nm, and III-Phosphide semiconductors, such as InGaP, have refractiveindices of about 3.7 at 600 nm. Contacts 304 and 306 may be formed froma solder, such as AuSn, AuGa, AuSi or SAC solders.

FIG. 3B is a diagram of an example light emitting semiconductorstructure 302 that may be included in the LED die 230 of FIG. 3A. Theillustrated example is a flip chip structure. However, one of ordinaryskill in the art will understand that the embodiments described hereinmay be applied to other types of LED designs, such as vertical, lateral,and multi-junction devices.

In the example illustrated in FIG. 3B, the light emitting semiconductorstructure 302 includes a light emitting active region 312 disposedbetween a semiconductor layer or region of n-type conductivity (alsoreferred to as an n-type region) 310 and a semiconductor layer or regionof p-type conductivity (also referred to as a p-type region) 314.Contacts 316 and 318 are disposed in contact with a surface of the lightemitting semiconductor structure 302 and electrically insulated from oneanother by a gap 320, which may be filled by a dielectric material, suchas an oxide or nitride of silicon (i.e., SiO₂ or Si₃N₄). In theillustrated embodiment, contact 316 (also referred to as a p-contact) isin direct contact with a surface of the p-type region 314, and thecontact 318 (also referred to as an n-contact) is in direct contact witha surface of the n-type region 310. Although not shown in FIG. 3B, adielectric material, such as disposed in the gap 320, may also line sidewalls of the light emitting active region 312 and p-type region 314 toelectrically insulate those regions from the contact 318 to preventshorting of the p-n junction.

The n-type region 310 may be grown on a growth substrate and may includeone or more layers of semiconductor material. Such layer or layers mayinclude different compositions and dopant concentrations including, forexample, preparation layers, such as buffer or nucleation layers, and/orlayers designed to facilitate removal of the growth substrate. Theselayers may be n-type or not intentionally doped, or may even be p-typedevice layers. The layers may be designed for particular optical,material, or electrical properties desirable for the light emittingregion to efficiently emit light. Like the n-type region 310, the p-typeregion 314 may include multiple layers of different composition,thickness, and dopant concentrations, including layers that are notintentionally doped, or n-type layers. While layer 310 is describedherein as the n-type region and layer 314 is described herein as thep-type region, the n-type and p-type regions could also be switchedwithout departing from the scope of the embodiments described herein.

The light emitting active region 312 may be, for example, a p-n diodejunction associated with the interface of p-region 314 and n-region 310.Alternatively, the light emitting active region 312 may include one ormore semiconductor layers that are doped n-type or p-type or areun-doped. For example, the light emitting active region 312 may includea single thick or thin light emitting layer. This includes ahomojunction, single heterostructure, double heterostructure, or singlequantum well structure. Alternatively, the light emitting active region312 may be a multiple quantum well light emitting region, which mayinclude multiple quantum well light emitting layers separated by barrierlayers.

The p-contact 316 may be formed on a surface of the p-type region 314.The p-contact 316 may include multiple conductive layers, such as areflective metal and a guard metal, which may prevent or reduceelectromigration of the reflective metal. The reflective metal may besilver or any other suitable material, and the guard metal may be TiW orTiWN. The n-contact 318 may be formed in contact with a surface of then-type region 310 in an area where portions of the active region 312,the n-type region 310, and the p-contact 316 have been removed to exposeat least a portion of the surface of the n-type region 310. The sidewallof the exposed mesa or via may be coated with a dielectric to preventshorting. The contacts 316 and 318 may be, for example, metal contactsformed from metals including, but not limited to, gold, silver, nickel,aluminum, titanium, chromium, platinum, palladium, rhodium, rhenium,ruthenium, tungsten, and mixtures or alloys thereof. In other examples,one or both contacts 316 and 318 may be formed from transparentconductors, such as indium tin oxide.

The n-contact 318 and p-contact 316 are not limited to the arrangementillustrated in FIG. 3B and may be arranged in any number of differentways. In embodiments, one or more n-contact vias may be formed in thelight emitting semiconductor structure 302 to make electrical contactbetween the n-contact 318 and the n-type layer 310. Alternatively, then-contact 318 and p-contact 316 may be redistributed to form bond padswith a dielectric/metal stack as known in the art. The p-contact 316 andthe n-contact 318 may be electrically connected to the contacts 304 and306 of FIG. 3A, respectively, either directly or via another structure,such as a submount.

FIG. 3C is a diagram of an example LED 330. In the example illustratedin FIG. 3C, the LED 330 includes an LED die 230. A wavelength convertingstructure 218 is disposed in direct contact with a surface 352 of theLED die 230. A thin film reflector 360, such as a Bragg reflector, maybe a coating on side surfaces 370 of a structure formed from the LED die230 and the wavelength converting structure 218 such that the thin filmreflector 360 may be in direct contact with side surfaces of both thewavelength converting structure 218 and the LED die 230. The wavelengthconverting structure 218 having properties such as described above hassufficient CTE match with the thin film reflector 360 such that the thinfilm reflector 360 does not crack when in direct contact with thewavelength converting structure 218. Further, the wavelength convertingstructure 218 may have a roughness of 100 nm or less, as described indetail above, which is sufficient for use with the thin film reflector360 such that un-converted pump light and converted light do not leakthrough the side surfaces 370 and through the thin film reflector 360.

Having described the embodiments in detail, those skilled in the artwill appreciate that, given the present description, modifications maybe made to the embodiments described herein without departing from thespirit of the inventive concept. Therefore, it is not intended that thescope of the invention be limited to the specific embodimentsillustrated and described.

What is claimed is:
 1. A light emitting device (LED) comprising: a lightemitting semiconductor structure comprising a light-emitting activelayer disposed between an n-layer and a p-layer; and a wavelengthconverting structure having a first surface in direct contact with thelight emitting semiconductor structure, a second surface opposite thefirst surface, and a side surface connecting the first and secondsurfaces, the wavelength converting structure comprising a binder ormatrix material, particles of a non-luminescent material, and phosphorparticles, the wavelength converting structure having a concentration ofgreater than 60% by volume of the non-luminescent material and phosphorparticles, the side surface of the wavelength converting structurehaving a roughness of less than 100 nm.
 2. The LED of claim 1, whereinthe first surface of the wavelength converting structure is in directcontact with the light emitting semiconductor structure withoutintervening adhesive.
 3. The LED of claim 1, comprising a non-metallic,thin-film reflector in direct contact with the side surface of thewavelength converting structure.
 4. The LED of claim 3, wherein thelight emitting semiconductor structure has a first surface, a secondsurface opposite the first surface, and a side surface connecting thefirst and second surfaces of the light emitting semiconductor structure,and the non-metallic, thin-film reflector in direct contact with theside surface of the light emitting semiconductor.
 5. The LED of claim 3,wherein the thin film reflector is a Bragg reflector.
 6. The LED ofclaim 5, wherein the Bragg reflector has a thickness of 1-10 microns. 7.The LED of claim 3, wherein both the wavelength converting structure andthe thin film reflector have a coefficient of thermal expansion (CTE) ofbetween 6 and 20 ppm/C.
 8. The LED of claim 1, wherein the binder ormatrix material is silicone.
 9. The LED of claim 8, comprising anon-metallic, thin-film reflector in direct contact with the sidesurface of the wavelength converting structure.
 10. A light emittingdevice (LED) comprising: a light emitting semiconductor structure havinga first surface, a second surface opposite the first surface, and a sidesurface connecting the first and second surfaces, the light emittingsemiconductor structure comprising a light-emitting active layerdisposed between an n-layer and a p-layer; a wavelength convertingstructure having a first surface in direct contact with the secondsurface of the light emitting semiconductor structure, a second surfaceopposite the first surface, and a side surface connecting the first andsecond surfaces, the wavelength converting structure comprisingsilicone, particles of a non-luminescent material, and phosphorparticles, the wavelength converting structure having a concentration ofgreater than 60% by volume of the non-luminescent material and phosphorparticles; and a non-metallic, thin-film reflector in direct contactwith the side surface of the wavelength converting structure.
 11. TheLED of claim 10, wherein the first surface of the wavelength convertingstructure is in direct contact with the light emitting semiconductorstructure without intervening adhesive.
 12. The LED of claim 10, whereinthe non-metallic, thin-film reflector is in direct contact with the sidesurface of the light emitting semiconductor structure.
 13. The LED ofclaim 10, wherein the thin film reflector is a Bragg reflector.
 14. TheLED of claim 13, wherein the Bragg reflector has a thickness of 1-10microns.
 15. The LED of claim 10, wherein both the wavelength convertingstructure and the thin film reflector have a coefficient of thermalexpansion (CTE) of between 6 and 20 ppm/C.
 16. The LED of claim 10,wherein the side surface of the wavelength converting structure has aroughness of less than 100 nm.
 17. The LED of claim 15, wherein the thinfilm reflector is a Bragg reflector.
 18. The LED of claim 17, whereinthe Bragg reflector has a thickness of 1-10 microns.
 19. A lightemitting device (LED) comprising: a light emitting semiconductorstructure having a first surface, a second surface opposite the firstsurface, a side surface connecting the first and second surfaces, thelight emitting semiconductor structure comprising a light-emittingactive layer disposed between an n-layer and a p-layer; a wavelengthconverting structure having a first surface in direct contact with thesecond surface of the light emitting semiconductor structure withoutintervening adhesive, a second surface opposite the first surface, aside surface connecting the first and second surfaces and a coefficientof thermal expansion (CTE) of between 6 and 20 ppm/C, the wavelengthconverting structure comprising silicone, particles of a non-luminescentmaterial, and phosphor particles, the wavelength converting structurehaving a concentration of greater than 60% by volume of thenon-luminescent material and phosphor particles; and a non-metallic,thin-film reflector in direct contact with the side surface of thewavelength converting structure, the non-metallic, thin-film reflectorhaving a coefficient of thermal expansion (CTE) of between 6 and 20ppm/C.
 20. The LED of claim 19, wherein the thin film reflector is aBragg reflector.